Electrical measuring instrument.



\ P. A. CAMPBELL.

ELECTRICAL MEASURING msmumam.

APPLICATION FlLED JAN- 3, 19).

' Patented June 29,1915.

3 SHEETS-SHEET 1- HHH Mim P. A. CAMPBELL.

ELECTRICAL MEASURING INSTRUMENT. APPLICATION FILED IAN.3, 1910.

hmfififio I Patented June 29, 1915.

3 SHEETSSHEET 2.

. WITNESSES: I IVENTOR BY MQCYM v ATTORNEY P. A. CAMPBELL. ELECTRICAL MEASURING INSTRUMENT. APPLICATION FILED JAN-3. I910. 1 145636 Patented June 29, 1915.

3 SHEETSSHEET 3.

2.9 \\\"II/ a0 54/ 50 I V v 5I WITNESSES: INVENTOR Y mgb bd v UNITED s'rarae Parana orrr.

PERCY A. GAMPBELL, F NEWARK, NEW JERSEY, ASSIGNOR T0 WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

EL CTRICAL MEASURING INSTRUMENT- the resistances of incandescent lamp filadetermined.

ments may be expeditiously and accurately In the manufacture of electric incandescent lamps in which the filaments comprise p a plurality of sections that are joined or connected at their extremities, it is highly desirable to ascertain the resistances of the filament sections before they are placed 1n lamps, in order that'all of the sections employed in each lamp may be of substantially the same specific resistance- When lamps are constructed in this manner, all of the filament sections are heated to substantially the same temperature and degree of incandescence, and, consequently, they have substantially uniform. life. By. properly rating the lamps, they will have greater and more uniform life than they would have if the filaments were not of uniform resistance.

It is the specific object of the present invention to provide an instrument for conveniently, expeditiously and accurately measuring the resistances of the sections of incandescent lamp filaments.

The invention is illustrated in the accompanying. drawings, Figure 1 of which is a plan view of an instrument embodying the same. Fig. 2 is a View, in'end elevation, of the instrument, and Fig. 3 is a diagrammatic view illustrating its circuit connections.

The method of measuring practised by the instrument is that commonly known as the Thompson double bridge method, because of the accuracy of the results that may be obtained thereby. U

The instrument comprises a base 1 having a horizontally drilled passage 2 in one of its edges and two vertically drilled recesses 3 and 4 extending downwardly into the base from its upper. face and communicating with the passage-2. 'The passage 2 is provided for the purpose of permitting of ready cleaning of the recesses '3 and 4. Secured Specification of Letters Patent.

Patented-June29, 1915.

Application filed January 3, 1910. Serial No. 536,117.

upon the upper face of the base, and along one edge thereof, is a glass plate 5 having apertures 6 and 7 directly above and corresponding to the recesses 3 and 4 in the base. Extendingcentrally across the apertures 6 and 7 in the plate 5 are partitions 8 and 9 carrying wire stops 10 and 11 that project above the surface of the plate 5-to assist in positioning the filament sections during the measurement of their resistances. Other stops 12 are alsomounted in the upper face of the plate 5 for the same purpose.

Secured upon the upper face of the base 1, and a one side of the glass plate 5, are bearing posts 13 and 14, between which a two-part insulating block 15 *is pivotally mounted. Secured in the block 15, and projecting from one side thereof, are four arms 16, 17, 18 and 19, that are arranged in pairs,

the arms 16 and 17, which constitute one pair, being longer than, and mounted directly above, the arms 18 and 19, constituting the other pair. The said arms are all insulated from each other, and are secured in invariable relation to each other near their outer ends in an insulating block 20. To the outer ends of the arms 16 to 19, .inclusive,-are secured terminal members 21, 22,

23 and 24, respectively, having forked extremities preferably composed of copper, or of other material which may be amalgamated, or for which mercury possesses a high degree of capillary attraction, the spaces between the prongs of the forked terminal membersbeing filled with mercury.

The inner .faces of the prongs of the terminal members diverge'from each other, so that the mercury is maintained in the upper ends of the spaces between them by capillary action.

' The arms 16 to 19, inclusive, and the terminal devices carried thereby, are so constructed and. arranged that, when the. block 15 is rotated, theterminal devices 21 to 24, 0O

inclusive, will enter the apertures 6 and? in the plate 5, the members 21 and 22 enter; ing the aperture6 upon opposite sides of the partition8, and the members 23 and 24 en: tering the aperture 7 upon opposite sides of the partition 9. Also mounted in and projecting through the insulating block 1.5,

is an L-shaped arm 25, the forward freeend of which is covered with leather 26 and is conveniently disposed to permit of efl'e'ctinigmanual rotation of the block 15. The movementsLof the arm 25 and of the block 15 and its associated parts are limited by means of an adjustable stop 27 that is threaded in the arm 25 and is adapted to engage a cork or other suitable cushion 28 that is secured upon the upper face of the base 1. Secured to the front end of the arm 25 is a terminal member 29 that is adapted to project into a cup 30 containing mercury and constituting the other circuit terminal. At the rear end of the arm 25 is a smaller L-shaped arm 31 that extends substantially vertically through the arm 25 and projects laterally therefrom, its lower end normally resting upon a cushion 32 upon the upper face of the base 1.

r The parts are normally maintained in the too rapid movement thereof.

A filament section 40 is placed for resistance measurement upon the glass plate 5,

substantially as illustrated in Fig. 1, and the length of a predetermined portion thereof,

the resistance of which is to be measured, is accurately determined by the distance between a plate or stop 41 and the stops 10 and 11, of the terminal members 22 and 23. The stop 41 is carried by a block 42 that is threaded upon a rod or shaft 43 having bearings at its ends respectively in the bear ing post 14 and in a post 44 that is secured. to one end of the base 1, the outer end of the rod being flattened to permit of ready turning thereof by means of a wrench or other tool. By this means, the position of the stop 41 may be accurately determined, and it is maintained firmly against the glass plate 5 so that the filament sections cannot get between it and the plate 5, by means of a screw 45 that is threaded in the block 42 and bears upon a plate 46' secured to the upper face of the base 1.

In order to facilitate handling of the filament sections and of placing and maintaining them in their correct positions during the resistance measurements, a blast of air is directed, preferably at a' slight angle to the vertical, upon the upper face of the glass plate 5 between the stops 10 and .11 by means of a pipe 47 that communicates with any suitable source of air pressure (not shown). The air pressure should be suflicient to force the legs of the filament outwardly against the stops 10 and 11. This is: regarded as a very important feature of the lnstruments, because it facilitates and insures accurate positioning of the filament sections.

The electrical connections of the instrument are illustrated in Fig. 3, in which it and 19 and the resistances 49 and 50. The

arms 17 and 18 are connected respectively to the terminals of very high resistances 53 and 54, between approximately the middle or other suitable intermediate points of which a galvanometer 55 is connected, the remaining terminal of the resistance 53 being connected to one terminal of the resistance 49, and the remaining terminal of the resistance 54 being adapted to be connected to a suitable intermediate point of re sistance 50, or to its other terminal.

In the operation of thedevice, a filament section 40 is placed in position upon the plate 5 and its legs are forced against the stops 10' and 11 by the blast of air from the pipe 47. The free end of the arm 25 is then manually depressed so as to cause the terminal members 21 to 24, inclusive, to enter the apertures in the plate 5 with the vices 22 and 23, no. difference of potential will exist between the terminals of the gal vanometer 55, and, consequently, the galvanometer will indicate no deflection. If,

however, the resistance included between the terminals of theresistances 53 and 54 is not the same as that of the portion of the filament section between the terminal de- 1 An instrument of the character described comprising a plurality of movable 7 ing a forked memberthe prongs of which terminal devices that carry bodies of mercury, a base having recesses forv the recepetion of the terminal devices, and means for 2. An instrument of-the character described comprising a plurality of movable forked terminal devices, mercury supported in and carried by the said devices, a base 1 having recesses for the reception of the terminal devices, and means for normally maintaining the terminal devices out ofthe sald recesses.

3. An instrument of the character de- 5.scrib ed comprising a plurality of movable terminal devices, a base having recesses for the reception of the terminal devices, means for normally maintaining the terminal devices out of the said recesses, and means for zoestablishing the circuit to the terminal devices when they occupy the recesses.

4. An electrical terminal device comprising a forked member and mercury engaging and carried by the'prongs of the member.

5. An electrical terminal device comprisdiverge, and mercury engaging and carried I by the prongs of the member.

6. An electrical terminal device compris ing a forked member the prongs of-which diverge and are amalgamated, and mercury getween and carried by the prongs of the ork.

' 7. An electrical terminal device having spaced side members and a liquid conductor located between, engaging and carried by the said side members. V

{8. An electrical terminal device having spaced amalgamated side members and mercury located between and carried by the said members. ,7

9. An 'el'ectrical'terminal device having ters the recess.

spaced side members .and mercury located between, engaging and carried by the said members. w

10. An instrument for operating upon filaments comprising a base, a plurality of terminal devices, and means for directing an air blast upon the base to retain a filament in position to be engaged by the terminal devices.

11. An instrument'for operating upon filaments comprising a base, ,a plurality of terminal devices, stops carried by the base, and means for directing an air blast obliquely upon the base to retain a filament against the stops and in position to be engagedb'y the terminal devices.

12. An instrument for operating upon filaments comprising a movable terminal de vice, a base having a recess for the reception of the terminal device, and means for-retaining a filament in position to be engaged by the movable terminal device when it en- 13. An instrument for operating upon filaments comprising a plurality of movable forked terminal devices, mercury carried in and supported by the said devices, a base having recesses for the reception of the terminal devices,.means for normally maintaining the terminal devices out of the said recesses, and means for retaining a filament in position to be engaged by the movable terminal devices when they enter the re cesses.-

In testimony whereof, I have hereunto subscribed my name this 24th day of December, 1909.

PERCY A. CBELL. 'Witnesses:

A. Yomvonomr,

CHARLES E. Kenny. 

